This invention relates to a biomedical electrode that can function in each of the following principal uses of biomedical electrodes: electrosurgical, cardiac monitoring, pacing, and defibrillation, and various means of measuring mammalian tissue impedance. As such the biomedical electrode of the present invention is universally functional.
Biomedical electrodes have traditionally been characterized by the type of medical activity that uses them as a transducer at the skin of a mammalian patient, to convert ionically transmitted electrical signals inside the body to electronically transmitted electrical signals outside the body, or to convert electronically transmitted electrical signals outside the body into ionically transmitted electrical signals inside the body.
Electrosurgical generators require a biomedical electrode functioning as a dispersive electrode to recover the electrical signals introduced into the body during surgery. Typical dispersive plate electrodes are disclosed in U.S. Pat. Nos. 4,539,996; 4,387,714; 4,166,465; and 4,269,189.
Cardiac monitoring electrodes, also known as electrocardiography (ECG) electrodes, require a biomedical electrode to detect faint electrical signals emanating from the mammalian heart as a means to monitor the condition of the heart. Such electrodes convert the ionic current in the body to electronic current to be processed by the instrumentation. Typical monitoring electrodes are disclosed in U.S. Pat. Nos. 4,846,185; 5,489,624 and 5,520,180.
While cardiac monitoring electrodes are used to receive electrical signals that originate within a mammalian body, electrosurgical dispersive electrodes, pacing electrodes, and defibrillation electrodes are used to impart and/or receive electrical signals that originate in a piece of external electrical equipment.
Pacing electrodes introduce electrical energy into the mammalian body as a therapy for a weakened, irregular, or slow heart. Typical pacing electrodes are disclosed in U.S. Pat. No. 5,330,526.
Respiration monitoring and cardiac output monitoring electrodes measure transthorasic impedance by passing a current in the microamperes range. Sometimes, the defibrillation/pacing signal is also used to measure impedance.
Defibrillation electrodes introduce a massive, abrupt amount of electrical energy into the mammalian body to induce a correction to the heart in a lifesaving effort to restore proper heartbeat of a heart muscle in ventricular fibrillation. Defibrillation electrodes can also be used in a related application known as cardioversion, whereby a massive, abrupt amount of electrical energy is used to correct persistent irregular heart rhythms, such as atrial fibrillation. In this case it is crucial to synchronize the delivered electrical shock to a specific portion of the repeated ECG signal.
Attempts have been made to create multi-functional electrodes to perform a desired combination of the above activities, typically in some combination of pacing, monitoring, and defibrillation. A mammalian patient who has severe heart or other disease needs monitoring to determine the type and proper amount of heart therapy, including the possibility of pacing a heart over a period of time, or shocking the heart to restore a normal rhythm. Typical multi-functional biomedical electrodes are disclosed in U.S. Pat. No. 4,895,169(Heath); U.S. Pat. No. 5,571,165 (Ferrari); and those electrodes marketed by Cardiotronics of Kimberly Clark Corporation; Katecho; Zoll Medical Devices Corporation; and Meditrace of Tyco Laboratories.
No biomedical electrode has been shown to be able to perform the dispersive electrode function with any of the other three functions especially without adverse effects such as skin damage. But the most significant advance in dispersive electrodes in recent years, as disclosed in U.S. Pat. No. 5,836,942 (Netherly et al.), provides for reduced edge effect using a lossy dielectric material to more evenly distribute the current emerging from the mammalian patient over the entire conductor surface of the dispersive electrode.
The art needs a multi-functional electrode that can function in each of the principal ways, i.e., a universally functional electrode. The art needs a universally functional electrode that provides reliable transduction at the skin of a mammalian patient for each of the types of use for biomedical electrodes. The art needs a universally functional electrode that functions individually or in any combination of two, three, four, or five of the types of use for biomedical electrodes.
One aspect of the present invention is a universally functional biomedical electrode, comprising an electrode having a resistive element that reduces edge effect by a redistribution of current within the electrode and in mammalian tissue contacting the electrode.
Another aspect of the present invention is A method of using the electrode, comprising the steps of (a) adhering at least one above-identified electrode to mammalian tissue of a patient; and (b) performing at least one biomedical function selected from the group consisting of monitoring, defibrillation, pacing, electrosurgical dispersing, impedance measuring, and combinations thereof.
A third aspect of the present invention is a biomedical electrode, comprising at least one electronic conductor in contact with an ionically conductive material that interfaces mammalian tissue for exchanging electromagnetic energy, the ionically conductive material containing: (a) at least one highly resistive material, having an impedance that is substantially higher than that of the ionically conductive material; (b) at least one of the said highly resistive material(s) being substantially coplanar with the conductor surface; and (c) the highly resistive material having a geometry, shape and apertures selected to alter the current density profile reaching an interface between the electrode and mammalian tissue.
A feature of the biomedical electrode of the present invention is the ability to both monitor and pace a mammalian heart.
Another feature of the biomedical electrode of the present invention is the ability to both monitor and defibrillate a mammalian heart.
Another feature of the biomedical electrode of the present invention is the ability to both defibrillate and pace a mammalian heart.
Another feature of the biomedical electrode of the present invention is the ability to monitor, pace, and defibrillate a mammalian heart.
Another feature of the biomedical electrode of the present invention is the use of the same biomedical electrode in one instance for electrosurgery and in another instance to both monitor and pace a mammalian heart, even though electrode placement criteria sometimes discourages use of the electrode for all three functions concurrently.
Another feature of the biomedical electrode of the present invention is the use of the same biomedical electrode in one instance for electrosurgery and in another instance to both monitor and defibrillate a mammalian heart, even though electrode placement criteria sometimes discourages use of the electrode for all three functions concurrently.
Another feature of the biomedical electrode of the present invention is the use of the same biomedical electrode in one instance for electrosurgery and in another instance to both defibrillate and pace a mammalian heart, even though electrode placement criteria sometimes discourages use of the electrode for all three functions concurrently.
Another feature of the biomedical electrode of the present invention is the use of the same biomedical electrode in one instance for electrosurgery and in another instance to monitor, pace, and defibrillate a mammalian heart, even though electrode placement criteria sometimes discourages use of the electrode for all functions concurrently.
Another feature of the biomedical electrode of the present invention is the use of the same biomedical electrode in all of the combination of uses cited above and including diagnostic measurements such as dielectric properties of the mammalian tissue.
An advantage of the biomedical electrode of the present invention is the reduction of inventory for medical care facilities by the availability of a single biomedical electrode that can reliably perform all types of biomedical electrode activities identified above.
Another advantage of the biomedical electrode of the present invention is the ability to minimize burns and other tissue damage to skin of a mammalian patient during usage in pacing, defibrillation, and/or electrosurgery.
Another advantage of the biomedical electrode of the present invention is the ability to reduce the extreme discomfort experienced by a mammalian patient during usage of the electrode for external pacing and following cardioversion.
Other features and advantages will become apparent in discussion of the embodiments of the invention in relation to the following drawings.